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View Full Version : [How To] Design a ported box

seth350
11-26-2005, 06:28 PM
Now for the other part of my write up....

Slot Ported Boxes

Ported boxes are similar to sealed boxes in the way you calculate the airspace.
You still start out finding out how much cuft you need and then going from there.

Lets begin.....

Lets say your sub needs 3.5cuft ported and you want it ported at 33hz.

You first begin by finding what measurments will give you 3.5cuft.
To calculate for cuft, read my other article for instructions on how to do it.

WxHxD
34"x18"x13" = 3.56cuft Close enough!

Ok you have your dimensions, and your net volume now time for the port.

I recommend using a program like WinISD for this. Its quick and easy to do.
Punch in the parameters and we get this....

WxHxL
3"x18"x30.5" = 33.66hz

Now you have decided on how big of a port you want. Now its time to calculate its displacment.

#1 What you do is you take the length (30.5") and substract .75 from it. = 29.75
#2 Then you multiply that by your height (29.75x18=535.5)
#3 Then take your width (3") and add .75 it (3.75) then multiply by what you got in step #2.(535.5x3.75=2008.125)
#4 Now take the number you got from #3 and divide it by 1,728 (2008.125/1,728=1.162109375) then do significant figures and you get 1.16cuft.

Now you have your port displacment and now you need your sub disp.
Lets say your sub needs .18cuft displacment.

Ok now here is what you do.

Now, you have to make adjustments to your dimensions in order to get 3.56cuft after you add the port and sub.
So now you take the measurments you started out with and adjust the height and width until you get 4.90cuft.
Which you should end up with 36.75"x18"x16" and that gives you 4.88053cuft and then do significant figures and you get 4.90cuft.
You dont change the height b/c then it would mess with the disp of the port and also cause it to change the tuning and it gets confusing from there. So do not change the height when adjusting your measurments
Now you build the box to those dimensions, not the dimensions you started out with.
You use the new measurments because then when you put in the port and the sub you have 3.56cuft left for the sub. Which is what it called for!
Now you have designed your own box and its done right! Hopefully........

Hope this helped out the noobs, and anyone else who needed it.

danteBirosel
11-26-2005, 06:30 PM
:bowdown: :bowdown: :bowdown:

great mini tutorial!

XtrmAudioCncpts
11-26-2005, 06:35 PM

seth350
11-26-2005, 06:37 PM
Yeah but mine is more simplified I think and not as intimidating to noobs as that one is.

Oh well, guess it was all a waste then.

PepsiFiend69
11-26-2005, 07:50 PM
what happens say if you're making a 1 chambered box for 2 subs, with 1 port, does the port stay the same size, or does it need to be doubled?

bimma85
11-26-2005, 07:53 PM
Yeah but mine is more simplified I think and not as intimidating to noobs as that one is.

Oh well, guess it was all a waste then.
but this may help all the noobs to lazy to search lol, at least for a few minutes ;)

seth350
11-26-2005, 07:55 PM
what happens say if you're making a 1 chambered box for 2 subs, with 1 port, does the port stay the same size, or does it need to be doubled?

Your port wont change, however you will need to compensate for both of the subs displacment.

That volume is how much you need in order to have the needed amount for both of the subs.
You then would adjust your width and depth until you get that amount. Then build to those measurments.

PepsiFiend69
11-26-2005, 07:56 PM
thanks!

seth350
11-26-2005, 07:57 PM
but this may help all the noobs to lazy to search lol, at least for a few minutes ;)

Unless a mod stickys it......which is what Im hoping.
Make it really easy then for all of us.

seth350
11-26-2005, 07:57 PM
thanks!

Anytime :)

PowerNaudio
11-27-2005, 09:03 AM
seth350: thats a great way to explain displacements and enclosure calculations
but you should add how to fold a slotport.

could you explain it to this image in on you own words. plz
http://tinypic.com/hvcdac.jpg

http://tinypic.com/hvcdac.jpg

seth350
11-27-2005, 12:40 PM
Thats a really good diagram. :)

Basically, you can't get your port length by cutting port two walls and having their lengths equalling 40" long.

Instead you have to find the center point of the port and measure out 40" from the front to the center point and from the center point to the end.
Then you build your walls accordingly.

The diagram gives a great example on how to do that. :)

Omarvelous
11-27-2005, 01:14 PM
I don't think it was a waste, bu i do think atleast 1 of these threads should be given STICKY status

PowerNaudio
11-27-2005, 01:42 PM
Thats a really good diagram. :)

Basically, you can't get your port length by cutting port two walls and having their lengths equalling 40" long.

Instead you have to find the center point of the port and measure out 40" from the front to the center point and from the center point to the end.
Then you build your walls accordingly.

The diagram gives a great example on how to do that. :)

thanks for the compliment on the drawing, i tried to cover what you where explaining and added a little using a drawing.

yeah we need a sticky on how to do all the calculations for a ported enclosure.
that way the same questions wont get asked over and over.

PowerNaudio
11-27-2005, 02:08 PM
i try lol

seth350
11-27-2005, 02:24 PM
I know my way isnt the correct way but its gets pretty close.

But yes we do need a sticky with all the calculations.
Sorry if some of my calculations aren't the perfect way to do it, just trying to help atleast 1 person out.

matt_martin87
11-27-2005, 05:49 PM
Wow..I tried using that big formula and I ended up with a number in the hundreds:uhoh: And im in calculus right now so thats saying something..either I'm friggin retarded or this is a really really complex formula.

DBfan187
11-27-2005, 05:51 PM
Port Displacement

if it uses of the sides of the box for one side of its port wall, then:
(port height) x (port length-wood thickness) x (port width + wood thickness) / 1728

if the ports in the middle of the box, and has its own walls, then:
(port height) x (port length - wood thickness) x [port width + 2(wood thickness)] / 1728

seth350
11-27-2005, 06:30 PM
Port Displacement

if it uses of the sides of the box for one side of its port wall, then:
(port height) x (port length-wood thickness) x (port width + wood thickness) / 1728

if the ports in the middle of the box, and has its own walls, then:
(port height) x (port length - wood thickness) x [port width + 2(wood thickness)] / 1728

Which is what I said...:emb:

danteBirosel
01-15-2006, 02:15 AM
is this tutorial accurate?